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Template Inheritance

Theme types

Templates in SilverStripe are bundled into one of two groups:

  • Default Templates, such as those provided in mymodule/templates folder.
  • Theme templates, such as those provided in themes/mytheme/templates folders.

The default templates provide basic HTML formatting for elements such as Forms, Email, or RSS Feeds, and provide a generic base for web content to be built on.

Template types and locations

Typically all templates within one of the above locations will be nested in a folder deterministically through the fully qualified namespace of the underlying class, and an optional type specifier to segment template types. Basic template types include Layout and Includes, and a less commonly used Content type.

For instance, a class SilverStripe\Blog\BlogPage will have a default template of type Layout in the folder vendor/silverstripe/blog/templates/SilverStripe/Blog/Layout/BlogPage.ss.

Note: The optional type, if specified, will require a nested folder at the end of the parent namespace (SilverStripe\Blog) to the class, but before the filename (BlogPage).

Templates not backed by any class can exist in any location, but must always be referred to in code by the full path (from the templates folder onwards).

Nested Layouts through $Layout type

SilverStripe has basic support for nested layouts through a fixed template variable named $Layout. It's used for storing top level template information separate to individual page layouts.

When $Layout is found within a root template file (one in templates), SilverStripe will attempt to fetch a child template from the templates/<namespace>/Layout/<class>.ss path, where <namespace> and <class> represent the class being rendered. It will do a full sweep of your modules, core and custom code as it would if it was looking for a new root template, as well as looking down the class hierarchy until it finds a template.

This is better illustrated with an example. Take for instance our website that has two page types Page and HomePage.

Our site looks mostly the same across both templates with just the main content in the middle changing. The header, footer and navigation will remain the same and we don't want to replicate this work across more than one spot. The $Layout function allows us to define the child template area which can be overridden.

mysite/templates/Page.ss

<html>
<head>
    ..
</head>

<body>
    <% include Header %>
    <% include Navigation %>

    $Layout

    <% include Footer %>
</body>

mysite/templates/Layout/Page.ss

<p>You are on a $Title page</p>

$Content

mysite/templates/Layout/HomePage.ss

<h1>This is the homepage!</h1>

<blink>Hi!</blink>

If your classes have in a namespace, the Layout folder will be a found inside of the appropriate namespace folder.

For example, the layout template for SilverStripe\Control\Controller will be found at templates/SilverStripe/Control/Layout/Controller.ss.

Cascading themes

Within each theme or templates folder, a specific path representing a template can potentially be found. As there may be multiple instances of any matching path for a template across the set of all themes, a cascading search is done in order to determine the resolved template for any specified string.

In order to declare the priority for this search, themes can be declared in a cascading fashion in order to determine resolution priority. This search is based on the following three configuration values:

  • SilverStripe\View\SSViewer.themes - The list of all themes in order of priority (highest first). This includes the default set via $default as a theme set. This config is normally set by the web developer.
  • SilverStripe\Core\Manifest\ModuleManifest.module_priority - The list of modules within which $default theme templates should be sorted, in order of priority (highest first). This config is normally set by the module author, and does not normally need to be customised. This includes the $project and $other_modules placeholder values.
  • SilverStripe\Core\Manifest\ModuleManifest.project - The name of the $project module, which defaults to mysite.

ThemeResourceLoader

The resolution of themes is performed by a ThemeResourceLoader instance, which resolves a template (or list of templates) and a set of themes to a system template path.

For each path the loader will search in this order:

  • Loop through each theme which is configured.
  • If a theme is a set (declared with the $ prefix, e.g. $default) it will perform a nested search within that set.
  • When searching the $default set, all modules will be searched in the order declared via the module_priority config, interpolating keys $project and $other_modules as necessary.
  • When the first template is found, it will be immediately returned, and will not continue to search.

Declaring themes

All themes can be enabled and sorted via the SilverStripe\View\SSViewer.themes config value. For reference on what syntax styles you can use for this value please see the themes configuration documentation.

Basic example:

---
Name: mytheme
---
SilverStripe\View\SSViewer:
  themes:
    - theme_name
    - '$default'

Declaring module priority

The order in which templates are selected from themes can be explicitly declared through configuration. To specify the order you want, make a list of the module names under SilverStripe\Core\Manifest\ModuleManifest.module_priority in a configuration YAML file.

Note: In order for modules to sort relative to other modules, it's normally necessary to provide before: / after: declarations.

mymodule/_config.yml

Name: modules-mymodule
After:
  - '#modules-framework'
  - '#modules-other'
---
SilverStripe\Core\Manifest\ModuleManifest:
  module_priority:
    - myvendor/mymodule

In this example, our module has applied its priority lower than framework modules, meaning template lookup will only defer to our modules templates folder if not found elsewhere.

Declaring project

It is a good idea to define one of your modules as the project. Commonly, this is the mysite/ module, but there is nothing compulsory about that module name.

myapp/_config/config.yml

---
Name: myproject
---
SilverStripe\Core\Manifest\ModuleManifest:
  project: 'myapp'

About module "names"

Module names are derived their local composer.json files using the following precedence:

  • The value of the name attribute in composer.json
  • The value of extras.installer_name in composer.json
  • The basename of the directory that contains the module

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